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The Great Wharf Road Bridge, designed to provide a new access
for traffic into Canary Wharf in London's Docklands, has taken an important step
forward with the installation of the massive hydraulic cylinder that will raise
it to allow ships to pass through West India Quay.
Designed and manufactured by Hunger Hydraulic in Germany to a
brief from consulting engineers Bennett Associates, the 40-tonne ram is believed
to be the biggest installed in the UK. It will lift the north end of the 800
tonne structure 18.2 metres in order to provide a 15 metre x 15 metre navigable
passage beneath.
As part of the design process Bennetts were asked to investigate
various methods of lifting the 67-metre bridge, including the use of portable
equipment stored off site. One of the constraints required no part of the
structure to be within the dock itself. The mechanism being installed was chosen
because it met this criterion and was also simple and cost-effective, according
to project engineer Michael Thorogood.
Bennetts were responsible for the performance and design
specifications for the electrical, hydraulic and mechanical equipment required
to move the bridge, to accompany the exemplar design drawings used by the
contractor for construction detailing. The company also designed the systems for
pedestrian and traffic control.
The telescopic ram is a two-stage unit with 800mm and 910mm
cylinders inside an outer casing 12.9 metres long x 1.235 metres maximum outer
diameter. The ram is powered by three 132kW power packs to produce a maximum
operating thrust of 6581kN that will lift the bridge in 555 seconds and lower it
in 390 seconds. The bridge will still lift, but more slowly, even if only one of
the power packs is operating.
Trunnion bearings at the base of the ram and a pivoting
clevis at the top allow the ram to rotate approximately 7º either side of
vertical as it raises and lowers the bridge. The whole assembly stands in a
reinforced concrete chamber beneath the north abutment, where the master control
cabinets will also be located. A slave cabinet in the south abutment will
provide control and power to the vehicle and pedestrian barriers, as well as the
bridge lighting.
Architects for the project are Wilkinson Eyre, with Gifford
and Partners acting as lead consultant and structural engineer.
December 2003 |
